Ocular and systemic reactivity to isoprenaline in patients with insulin-dependent diabetes mellitus

There is experimental evidence of decreased β-adrenergic myocardial sensitivity in patients with insulin-dependent diabetes mellitus (IDDM). In the present study we hypothesized that the ocular response to isoprenaline, as a consequence of increased arterial vessel rigidity, might also be blunted in patients with IDDM. We therefore compared the correlation between systemic pulse pressure amplitude (PPA) and fundus pulsation amplitude (FPA) during intravenous isoprenaline administration in 11 otherwise healthy IDDM patients and 11 healthy control subjects. Ocular fundus pulsations were measured by a recently developed laser interferometric method. Isoprenaline increased PPA in both study groups in a dose-dependent way, but the response was significantly less in IDDM patients (at 0.8 μg min^-1: +38% in control subjects, +27% in IDDM patients, P < 0.05 between groups). Moreover, a dose-dependent increase in FPA was observed, which again was more pronounced in healthy subjects (at 0.8 μg min^-1: +45% in controls, +17% in IDDM patients, P < 0.005 between groups). The regression line between PPA and FPA was very close to the 45°line in healthy subjects, whereas it was significantly flattened in IDDM patients. In conclusion, linear regression between PPA and FPA during isoprenaline suggests arterial stiffening inpatients with IDDM. Hence, comparison of systemic PPA and FPA during isoprenaline provocation may be a useful method of estimating changes in arterial capacitance in patients with diabetes mellitus.